Devices designed to measure the amount of wear a specimen undergoes under certain conditions are well known. A common device applied a measurable load upon a test specimen which is a common contact with a companion surface and undergoes sliding motion relative thereto. The size of the wear scar is measured as a function of the load, relative sliding speed, and number of oscillations.
More recently, the study of the wear process occuring under conditions of impact loading has proven to be of significance, as mechanical components which make repeated contact under impulsive loads are typical of virtually all hardware designed for dynamic operation. In an increasing number of situations, such components operate without benefit of an external lubricant since solid lubricants, and self-lubricating or wear-resistant materials have been developed for such applications. In some cases the sliding wear resistance of these materials have been evaluated, but there has been little laboratory investigation of impact loading wear.
Several devices have been developed for studying impact wear, one being that of R. G. Bayer et al and described in 19 Wear pp. 343-354 (1972). This device fires test projectiles against a flywheel, normal impact occuring when the flywheel is stationary and sliding impact having force components normal and tangential to the flywheel occurring when it is rotating. The wear of the projectiles is measured by a profilometer after a given number of impacts. Since the projectile is unconstrained, it may be accelerated to varying degrees transverse to its direction of incidence during impact, so that there results a variable relative sliding velocity. This renders anaylsis of test data difficult. Furthermore, the device of Bayer et al provides no means for measuring the impact force pulse.
Another wear testing device is that of E. A. Pamfilov of the Soviet Union and described in 37 Zavodskaya Laboratoriya No. 5, pp. 620-621 (1971). His machine, by cams and springs, permits either impact or constant loading on a test specimen. No provision is made for measuring the impact impulse.
Other wear testing devices are deficient in that they do not provide for measurement of critical parameters such as impact force as a function of time and thus loading impulses, or permit combined normal incidence/sliding impact wear studies wherein the sliding contact is constant throughout the impact. They are also deficient in that it is quite difficult to maintain a constant impact force over a series of impacts as a test specimen undergoes wear.
Accordingly, it is an object of the present invention to provide a novel impact wear testing device capable of providing repetitive impacts to test specimens under either normal or sliding impact and in which the impact is easily measurable and reproducible.
It is also an object to provide such an impact wear testing device capable of maintaining the peak impact force at a desired magnitude.
Another object is to provide such a device providing convenient adjustability of the normal and tangential components of the load impulses applied to a test specimen and a constant relative sliding velocity between impacting materials during sliding impact.
A further object is to provide such a device providing a simple and direct measure of the impact force as a function of time.